1. Field of the Invention
The invention relates to a growth of deposited contaminants in processing systems, and in particular to a method and an apparatus for predicting a growth rate of deposited contaminants resulting from deposition of gaseous contaminants outgassed from a substance undergoing processing by one or more radiation beams. The invention also relates to a lithography system comprising a resist characterization system and a method for determining suitability of a resist for use in a lithography system.
2. Description of the Related Art
The desire of the semiconductor industry to manufacture ever smaller device structures, for example for use in integrated circuits (ICs), drives the development of lithography systems using very low wavelengths. Examples of such systems include but are not limited to extreme ultraviolet (EUV) lithography systems and charged particle lithography systems which use electron or ion beams to provide a pattern onto a target substrate surface.
Components within lithography systems are susceptible to contaminants that are progressively deposited on their surfaces during operation of the lithography system. In particular, contaminants may be formed by reaction of molecular fragments that are stuck on surfaces of the system under the influence of radiation within the lithography system. For example, under irradiation with EUV or charged particle beams, gaseous hydrocarbons may form a layer of carbon on exposed surfaces of system components. The result of the deposition of the gaseous compounds on the surfaces of system components is that the reliability and/or operational accuracy of the lithography system decreases with time. Eventually, the lithography system is incapable of operating within preset requirements, and the malfunctioning components need to be cleaned or replaced. However, both cleaning and replacement of components is time-consuming and expensive, and results in a significant increase in downtime of the lithography system.
A significant source of gaseous hydrocarbons in lithography systems is the resist layer that is placed on top of a substrate surface to be exposed and is subsequently exposed to radiation, e.g. EUV or charged particles, such as electrons. A suitable resist may be selected to limit the contamination in a lithography system caused by molecular fragments ejected from a resist, in particular due to exposure of the resist to radiation beams. However, presently used methods for characterizing resists are labor intensive and time consuming.